Inferior vena cava diameter | Change with respiration | Estimated right atrial pressure mmHg |
Small <1.5 cm | Collapse | 0 |
Normal 1.5–2.5 cm | Decrease by >50% | 5 |
Normal | Decrease by <50% | 10 |
Dilated >2.5 cm | Decrease by <50% | 15 |
Dilated with dilated hepatic veins | No change | 20 |